1. Field of Invention
The present invention relates to the field of image displaying, and more specifically, to a method for eliminating a seam between adjoined screens and an apparatus thereof.
2. Description of Prior Art
Recently, an increasing number of computers tend to the development of minimization with the continuous progress of electronic information technology. Accompanying the minimization, data-processing capability of computers has been enhanced, and a wider range of data types can be processed. Small-sized portable computers can be employed to fulfill such tasks as processing, storage and assembling for massive data, thereby significantly facilitating our daily work and life. For example, a notebook computer can be utilized to process stock information, map data and image data and display contents corresponding to the processing result on its screen. It is inevitable, however, that such computer minimization leads to a remarkable reduction in screen size, which makes it difficult for a user to gain a clear view of a reduced size screen. In particular to the above data requiring a high display quality, a reduced size screen cannot meet the requirement for display quality. This disables a user to acquire detailed information by a portable computer and accordingly causes inconvenience to the user. Take an example that when a user downloads map data via a notebook computer, the user cannot find a clear map with a large amount of information as he expects due to a small screen, such as an overview graph for determining roughly his location or a local detail graph for showing routes. Another example is that when a user processes stock data by a notebook computer, the user cannot obtain clearly huge stock information he desires due to a small screen, such as the overall tendency and detailed information on an individual share. In addition, computers can process multimedia data, such as video, with a gradually enhanced performance. Therefore, users can display videos by use of portable devices, for example, a notebook computer.
Although these portable devices are sufficiently capable of video data processing, with the limit on screen size, viewers cannot gain a visual enjoyment as that provided by a large screen. Thus, the video data display ability of a portable device is degraded. Moreover, in applying computers to project plotting and multi-window operation, a relatively large-sized screen is required to facilitate users' practice.
As can be seen from the above description, in the current progress of computer minimization, there is a contradiction between dimension reduction for an integral device and the need for a large screen. At present the contradiction is usually overcome by adopting screen-adjoining technology, which expands screen size by adjoining multiple screens without increasing the size of a device. Furthermore, in practical applications, there are many occasions with the need for a large-sized display, such as airports, train stations, athletic competitions and grand exhibitions, where a screen of a very large size is required to display information for people at a distance. On the other hand, the manufacture cost increases and production technique becomes more complex as the size of a screen expands. Therefore, the screen-adjoining technology is also applicable to occasions with the need for a large-sized display.
Screen-adjoining technology usually adopted in prior art include CRT adjoining, LCD adjoining and projector adjoining. Since a projector imposes a strict requirement on ambient light in that an image cannot be seen clearly with intense ambient light, the projector is applicable to only a narrow range of places, for example, indoors. As for CRT adjoining, LCD adjoining, the dominant problem is that there is a seam between adjoined screens no matter how close the screens are brought to each other. Specific cases are described as follows.
For a CRT, the display is effected by bombarding electrons to a fluorescence screen on the inner surface of a tube, which is made of a glass shell of certain thickness and evacuated into vacuum. The glass shell must have certain thickness to guarantee some strength. Therefore, the peripheral edge of a CRT tube can not be reduced to a width smaller than the thickness of its glass shell, which is usually 5 mm.
For a LCD, a complete screen is formed by injecting liquid crystals, whose color and grayscale can vary when applied to a voltage, into a small room and arranging a number of such rooms in an array. The edge of LCD is protected with packaging materials to prevent liquid crystal from leaking. The width of the edge is commonly not smaller than 5 mm.
As a result of the edge width of each of CRT and LCD, a seam appears inevitably in the process of adjoining screens. In prior art, the following techniques are used to eliminate a seam.
The First Method:
As shown in FIG. 1A to 1C, digital and optical image processing methods are employed at the edges of two screens. At first, the image on the edges of the screens is contracted by certain ratio. Then an optical lens is used to enlarge the contracted image while the image on the rest of the screens remains unchanged. Finally, the enlarged image is used to fill the gap caused by a seam during the adjoining process.
In the figures, the optical lens is denoted by reference numeral 140. Optical glass of different shapes and structures are used in FIG. 1A to 1C, respectively. Such optical glass can magnify an image by refracting light at its edge. The screen is denoted by reference numeral 30, and the dark part sandwiched by two screens 30 represents the seam between the screens. As shown in FIG. 1A to 1C, the light is refracted after penetrating the optical lens so as to magnify the image at the edge, thereby significantly reducing the visible width of the seam. This method can reduce the seam width, however, it has the following drawbacks.
(1) This method can only reduce the width of a seam other than completely eliminating it. Even when this method is adopted, the edge of a screen can be still visible and the thus formed seam is about 1 mm in thickness. This is roughly acceptable for a large screen display, while for the case of adjoining small screens in potable devices, it can be hardly accepted. Since small screens are generally adjoined for a portable device and the eyes of a user are close to the screen of the portable device, even a slight gap can appear obvious. This degrades image quality and further provokes the user's discontentment.
(2) If this method is adopted, since the optical lens placed on the screen is thick, the screen increases in size and mass while deteriorates in portability. For example, if two LCDs are combined, the seam between them is 10 mm wide, and the optical lens above them is 25 mm thick. The optical lens of such thickness will apparently adds the size and mass of the screen and makes it less convenient to carry.
(3) Since this method compresses and magnifies the image at the edge, the image itself will be damaged.
Besides, this method requires a precise calculation for the area of the edge image to be compressed and magnified, thereby making it complex to implement and unsuitable for practical applications.
The Second Method:
Frensnal lens is used in this method, in which the Frensnal lens magnifies the image on each of two screens by certain times to conceal the seam between the screens. As referenced to FIG. 2A, reference numeral 20 indicates two screens adjoined to each other, reference numeral 11 indicates the Frensnal lens, reference numeral 12 indicates a pressure-sensing plate, and reference numeral 13 indicates a flexible thin film. Although it can eliminate the seam, this method has the following disadvantages.
(1) In order to acquire a proper magnification factor, the Frensnal lens must be located a distance from the screens 20, otherwise the image cannot be magnified. This leads to a thicker display with an increased size, thereby worsening the portability of a device configured by this method.
(2) Bending the light through the Frensnal lens gives rise to a retrace phenomenon, therefore, in order to obtain the effect of a magnifier, fine zigzagged concentric circle strips must be spread over the lens surface. Such strips will adversely affect images and thereby image quality.
Besides, the processing cost for Frensnal lens is high, thus a high price hinders its application to a wide range.
The Third Method:
In terms of large screen application, as shown in FIG. 2B, the conventional technology as disclosed in the document Chinese Patent Application No. 01215900.X employs a means for display magnification by optical fiber (hereafter, referred to as fiber) transmission. The optical fiber 3 is used as a light-collecting opening, the other end thereof extends into an arcuate light-emitting head 2 to magnify images transmitted by each fiber. Reference numeral 1 denotes a holder, reference numeral 4 denotes a fiber support, and the fibers between the holder 1 and the fiber support 4 dangles independently of each other. This method is suitable for some occasions of image enlargement, and the apparatus has a large size.